Plainfield, NJ -- U.S. city in New Jersey Population (2000): 47829 Housing Units (2000): 16180 Land area (2000): 6.037708 sq. miles (15.637592 sq. km) Water area (2000): 0.001234 sq. miles (0.003195 sq. km) Total area (2000): 6.038942 sq. miles (15.640787 sq. km) FIPS code: 59190 Located within: New Jersey (NJ), FIPS 34 Location: 40.615352 N, 74.416070 W ZIP Codes (1990): Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Plainfield, NJ Plainfield